From: Subash Abhinov Kasiviswanathan Date: Fri, 22 Sep 2017 00:00:36 +0000 (-0600) Subject: net: qualcomm: rmnet: Fix rcu splat in rmnet_is_real_dev_registered X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=5c346525d3591cb032eca86d0f904cc01f1069ff;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git net: qualcomm: rmnet: Fix rcu splat in rmnet_is_real_dev_registered Xiaolong reported a suspicious rcu_dereference_check in the device unregister notifier callback. Since we do not dereference the rx_handler_data, it's ok to just check for the value of the pointer. Note that this section is already protected by rtnl_lock. [ 101.364846] WARNING: suspicious RCU usage [ 101.365654] 4.13.0-rc6-01701-gceed73a #1 Not tainted [ 101.370873] ----------------------------- [ 101.372472] drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c:57 suspicious rcu_dereference_check() usage! [ 101.374427] [ 101.374427] other info that might help us debug this: [ 101.374427] [ 101.387491] [ 101.387491] rcu_scheduler_active = 2, debug_locks = 1 [ 101.389368] 1 lock held by trinity-main/2809: [ 101.390736] #0: (rtnl_mutex){+.+.+.}, at: [<8146085b>] rtnl_lock+0xf/0x11 [ 101.395482] [ 101.395482] stack backtrace: [ 101.396948] CPU: 0 PID: 2809 Comm: trinity-main Not tainted 4.13.0-rc6-01701-gceed73a #1 [ 101.398857] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014 [ 101.401079] Call Trace: [ 101.401656] dump_stack+0xa1/0xeb [ 101.402871] lockdep_rcu_suspicious+0xc7/0xd0 [ 101.403665] rmnet_is_real_dev_registered+0x40/0x4e [ 101.405199] rmnet_config_notify_cb+0x2c/0x142 [ 101.406344] ? wireless_nlevent_flush+0x47/0x71 [ 101.407385] notifier_call_chain+0x2d/0x47 [ 101.408645] raw_notifier_call_chain+0xc/0xe [ 101.409882] call_netdevice_notifiers_info+0x41/0x49 [ 101.411402] call_netdevice_notifiers+0xc/0xe [ 101.412713] rollback_registered_many+0x268/0x36e [ 101.413702] rollback_registered+0x39/0x56 [ 101.414965] unregister_netdevice_queue+0x79/0x88 [ 101.415908] unregister_netdev+0x16/0x1d Fixes: ceed73a2cf4a ("drivers: net: ethernet: qualcomm: rmnet: Initial implementation") Signed-off-by: Subash Abhinov Kasiviswanathan Reported-by: kernel test robot Signed-off-by: David S. Miller --- diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c index 98f22551eb45..1e33aea59f50 100644 --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c @@ -51,10 +51,7 @@ struct rmnet_walk_data { static int rmnet_is_real_dev_registered(const struct net_device *real_dev) { - rx_handler_func_t *rx_handler; - - rx_handler = rcu_dereference(real_dev->rx_handler); - return (rx_handler == rmnet_rx_handler); + return rcu_access_pointer(real_dev->rx_handler) == rmnet_rx_handler; } /* Needs rtnl lock */